JPH07278517A - Acrylic emulsion composition for bonding woody material - Google Patents

Abstract

PURPOSE:To obtain a composition extremely useful as an adhesive for a woody substrate, especially the adhesive for veneer fancy plywood due to its excellence in resistances to warm water and boiling, etc., and further in working environment, etc., without using an amino-based condensation resin in combination therewith as opposed to a conventional adhesive. CONSTITUTION:This acrylic emulsion composition for bonding a woody material is obtained by blending an aqueous solution of ammonium zinc carbonate with an acrylic emulsion comprising a two-layer structure which is a copolymer of an aromatic vinylic monomer, an unsaturated carboxylic acid ester monomer, an acrylic monomer having amide group and an acrylic monomer having carboxyl group (a monocarboxylic acid) having -10 to +90 deg.C) Tg in a core layer and a copolymer of the aromatic vinylic monomer, the unsaturated carboxylic acid ester monomer and an acrylic monomer having the carboxyl group (a dicarboxylic acid) and having -50 to +20 deg.C Tg in a shell layer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention has compatibility with a bulking agent typified by wheat flour, which is commonly used in the production of decorative plywood using plywood as a substrate, and can be used when an adhesive is applied by a roll coater or the like. To an acrylic emulsion composition for wood adhesion, which is excellent in mechanical stability and coating workability and is excellent in hot water resistance and boiling resistance. More specifically, the name tree is 0.2
Regarding an acrylic emulsion used for making plywood with a single veneer plate sliced thinly to a thickness of ~ 3 mm, the leaching contamination of the adhesive on the veneer surface especially when adhering the thin veneer and the veneer plate after repeated cold heat test The present invention relates to an acrylic emulsion composition for wood adhesion that does not cause cracking.

[0002]

2. Description of the Related Art Conventionally, veneer decorative plywood is a urea-based condensation resin,
A blend of an amino-based condensation resin typified by a melamine-based condensation resin or a urea-melamine-based condensation resin and an extender typified by wheat flour, a vinyl acetate-based emulsion or a styrene-butadiene-based copolymer latex, wheat flour and an amino-based resin. Formulations of condensation resins have been used as adhesives.

[0003]

As is well known, veneer decorative plywood is widely used for floor materials, wall materials, furniture and the like. As the thickness of the veneer becomes thinner, there is a problem that the adhesive seeps out to the surface of the veneer and many dry cracks (fine cracks along the grain) occur. The adhesive for veneer typified by the adhesive containing the amino-based condensation resin and wheat flour is usually bonded by a hot press, but the adhesive strength such as hot water resistance and boiling resistance is excellent, but the adhesive is thermoset. Since the adhesive cured product is too hard because it is a functional resin, the thin veneer causes numerous cracks, and at the same time the amino-based condensation resin oozes and shines on the veneer surface, significantly reducing the commercial value and leaching There was a problem that it would not be a product if the amount was large. In addition, there is a problem that formalin released from the amino-based condensation resin adversely affects the human body in terms of working environment.

As a means for solving this problem, a method of blending a resin emulsion such as a thermoplastic vinyl acetate emulsion with an amino condensation resin and a flour mixture,
Attempts have been made to blend an elastomer with the amino-based condensation resin and the flour blend such as a styrene-butadiene copolymer latex having a low glass transition temperature (hereinafter abbreviated as Tg) and a pH in a neutral range. When the former vinyl acetate emulsion is used, a large amount of amino-based condensation resin must be blended in order to compensate for hot water resistance and boiling resistance (hereinafter abbreviated as water resistant adhesion). Although some improvement was observed as compared with the condensation resin, it was not satisfactory. Even when the latter styrene-butadiene copolymer latex is used, it is necessary to use a small amount of an amino-based condensation resin together in order to supplement the water-resistant adhesive strength, and the vinyl acetate-based emulsion was also used for cracking of the veneer. Although it is superior to the case, there was a limit as long as the amino-based condensation resin was used. When a styrene-butadiene copolymer latex is used, it lacks miscibility with wheat flour, and the composition has high viscosity and poor fluidity, resulting in poor coatability when applying the composition with a roll coater or the like. There was a problem that was extremely bad.

[0005]

Means for Solving the Problems The present inventors have found that an acrylic emulsion alone, which does not use an amino-type condensation resin, has miscibility with wheat flour and mechanical stability, cracks on a veneer, and soaks an adhesive. As a result of repeated studies on the development of an emulsion type adhesive that has contamination due to discharge and further has a water-resistant adhesive strength, the miscibility with wheat flour and the mechanical stability during coating with a roll coater etc. depend on the pH of the acrylic emulsion. However,
It has been found that the Tg of the acrylic emulsion and the generally-known functional group monomer are extremely effective in preventing cracking of the veneer, leaching contamination of the adhesive, and improving the water resistant adhesive strength. That is, it is most effective to copolymerize an acrylic monomer having an amide group in order to impart water-resistant adhesive strength, but the miscibility with wheat flour is significantly impaired.
This miscibility is imparted by copolymerizing an unsaturated carboxylic acid and adjusting it to a low pH range. In order to combine these two physical properties, it has a different phase structure like a core shell structure,
Using an acrylic monomer having an amide group in the core layer,
It has been found that the object is achieved by copolymerizing an unsaturated carboxylic acid in the shell layer. Further, it was found that the water-resistant adhesive strength is remarkably improved by metal-crosslinking the unsaturated carboxylic acid in the acrylic emulsion with a zinc compound.

That is, the present invention is as follows (1) to (6). 1) A core layer is an aromatic vinyl-based monomer, an unsaturated carboxylic acid ester monomer, an amide group-containing acrylic monomer and an unsaturated carboxylic acid copolymer, and a shell layer is an aromatic vinyl-based monomer, an unsaturated carboxylic acid ester monomer, and The amount of zinc ammonium carbonate (b) per 100 parts by weight of the solid content of the acrylic emulsion (a) having a two-layer structure, which is a copolymer of unsaturated carboxylic acid, is changed to the total amount of the acrylic monomer having a carboxyl group of the acrylic emulsion (a). On the other hand, an acrylic emulsion composition for wood adhesion, characterized in that 0.1 to 1.0 molar ratio of zinc is blended. 2) The monomer composition ratio of the core layer / shell layer of the acrylic emulsion (a) is 30 to 70/70 to 30 parts by weight, based on 100 parts by weight of the total amount of monomers, 1) The acrylic resin for bonding to wood. Emulsion composition. 3) The glass transition temperature (Tg) of the core layer of the acrylic emulsion (a) is −10 to + 90 ° C., and the glass transition temperature (Tg) of the shell layer is −50 to + 20 ° C. 1) Description Acrylic emulsion composition for wood adhesion. 4) The amount of the amide group-containing acrylic monomer and unsaturated carboxylic acid in the core layer of the acrylic emulsion (a) is 1 to 6 parts by weight per 100 parts by weight of the total amount of the core layer monomers, and the amount of unsaturated carboxylic acid in the shell layer is 1 to 10 parts by weight per 100 parts by weight of the total amount of monomers in the shell layer, 1) the acrylic emulsion composition for wood adhesion according to 1). 5) The acrylic emulsion composition for wood adhesion according to 1), wherein the pH of the acrylic emulsion (a) is adjusted to a range of 4 to 6 using ammonia water. 6) The zinc ammonium carbonate (b) is a transparent aqueous solution of water, ammonium carbonate, zinc oxide, and ammonia water having a concentration of 15 to 20% by weight and having a pH adjusted to 9 to 10. 1) The acrylic emulsion composition for wood adhesion according to 1).

Aromatic vinyl monomers used for emulsion polymerization of the acrylic emulsion (a) include styrene, α-methylstyrene, divinylbenzene and the like, and unsaturated ester monomers include methylmethacrylate, ethylacrylate, isobutylmethacrylate, tert-butyl methacrylate, vinyl acetate, acrylonitrile, isobutyl acrylate, n-butyl acrylate,
4 to 12 such as 2 ethylhexyl acrylate, 2 ethylhexyl methacrylate, and lauryl methacrylate
Examples thereof include acrylic acid or methacrylic acid ester having an alkyl group, and among them, styrene and / or a combination of methyl methacrylate and n-butyl acrylate is preferable from the viewpoint of economy and ease of emulsion polymerization.

As the acrylic monomer having an amide group, acrylamide, methacrylamide, maleimide,
N-methylol acrylamide, N-methylol methacrylamide, N-methoxymethyl acrylamide, N
-Isopropoxymethylacrylamide, N-butoxymethylacrylamide, N-isobutoxymethylacrylamide, N-octyloxymethylacrylamide, N
-Carboxymethyl acrylamide and the like are mentioned, and among them, N-methylol acrylamide and N-methylol methacrylamide having a methylol group are preferable from the viewpoint of adhesive strength, water resistance, warm water resistance and the like.

Examples of the acrylic monomer having a carboxyl group in the acrylic emulsion (a) include acrylic acid, methacrylic acid, crotonic acid as a monocarboxylic acid, and itaconic acid, maleic acid, fumaric acid as a dicarboxylic acid. Can be given. Among these acrylic monomers having a carboxyl group, a monocarboxylic acid is preferable from the viewpoint of copolymerizability with an acrylic monomer having an amide group in the core layer, stability during emulsion polymerization and mechanical stability.

On the other hand, the shell layer is preferably a dicarboxylic acid which is easily polymerized in an aqueous solution and which is present at the emulsion particle interface and is highly established. It is particularly effective for mechanical stability and compatibility with wheat flour of an acrylic emulsion in a low pH range. To work.
Specifically, acrylic acid or methacrylic acid is preferable as the monocarboxylic acid used for the core layer, and itaconic acid is preferable as the dicarboxylic acid used for the shell layer.

The monomer composition ratio of the core layer / shell layer of the acrylic emulsion (a) of the present invention is 10 total monomers.
It is 30 to 70/70 to 30 parts by weight in 0 parts by weight. It is preferably 50/50 parts by weight. When the monomer composition ratio is out of this range, the fluidity is poor due to lack of miscibility with wheat flour, and the coating property is poor when the composition is applied by a roll coater or the like, and a stable application state to an adherend is obtained. It becomes impossible to obtain it, or the stability due to mechanical shearing when the composition is applied with a roll coater or the like is deteriorated, and a stable applied state on the adherend cannot be obtained. In addition, the balance of water-proof adhesive strength cannot be maintained, which makes it unsuitable as a wood-bonding acrylic emulsion composition. As a specific example, when the shell layer is more than 70 parts by weight, the miscibility with wheat flour and the mechanical stability in a roll coater are improved, but the water-resistant adhesive strength is impaired. On the other hand, when the amount is less than 30 parts by weight, the water-resistant adhesive strength is obtained, but the miscibility with wheat flour is significantly reduced.

The acrylic emulsion (a) has a core layer Tg of -10 to + 90 ° C and a shell layer Tg of -50 to.
It is + 20 ° C. More preferably, the Tg of the core layer and the shell layer are 0 to + 60 ° C. and −40 to 0 ° C., and the Tg of the shell layer from the viewpoint of the film forming property of the emulsion at room temperature, the cracking property of the veneer, and the water resistant adhesive strength. The lower the better. When the core layer Tg is less than -10 ° C, the water-resistant adhesive strength cannot be obtained, and +9
If it exceeds 0 ° C, the stability during emulsion polymerization is insufficient, and in some cases there is a risk of gelation during emulsion polymerization, and the effect of preventing cracking of the veneer cannot be obtained. Also, the shell layer Tg is -50 ° C.
If it is less than 20%, the water-resistant adhesive strength is not obtained, and if it exceeds + 20 ° C., the water-resistant adhesive strength and the normal-state adhesive strength are decreased, and the effect of preventing cracking of the veneer is remarkably decreased.

The amount of the amide group- and carboxyl group-containing acrylic monomer in the core layer of the acrylic emulsion (a) of the present invention is 1 to 6 parts by weight per 100 parts by weight of the total amount of the core layer monomers. The amount is preferably 2 to 5 parts by weight in view of the stability during emulsion polymerization and the water resistant adhesive strength. When the amount is less than 1 part by weight, the water-resistant adhesive strength cannot be obtained, and when the amount is more than 6 parts by weight, the stability during emulsion polymerization is remarkably reduced and gelation occurs during the emulsion polymerization.

The amount of the acrylic monomer having a carboxyl group in the shell layer of the acrylic emulsion (a) is 1 to 10 parts by weight in 100 parts by weight of the total amount of the shell layer monomers.
It is preferably 2 to 5 parts by weight. When the amount is less than 1 part by weight, the miscibility with wheat flour is insufficient and the coatability becomes poor at the time of coating with a roll coater or the like, so that a stable coating state on the adherend cannot be obtained. In addition, the mechanical stability during coating also deteriorates. When the amount is more than 10 parts by weight, the emulsion polymerization rate is remarkably reduced, the polymerization is not completed within a predetermined emulsion polymerization time, the amount of residual monomer is increased, and the water-resistant adhesive strength is not obtained.

The pH of the acrylic emulsion (a) is adjusted to 4 to 6 with aqueous ammonia. More preferably 4.
It is 5 to 5.5. When it is less than 4, the above-mentioned mechanical stability cannot be obtained and a stable coating state on the adherend cannot be obtained. When it is more than 6, the miscibility with flour is remarkably lowered and the coatability deteriorates. A stable coating state cannot be obtained, which causes problems. 15-20% by weight of zinc ammonium carbonate (b)
A clear aqueous solution having a pH of 9 to 10 and a zinc concentration of 4 to 5% by weight in the aqueous solution.
Is.

This aqueous solution is prepared by mixing, for example, 112 parts by weight of distilled water with 12 parts by weight of zinc oxide and 20 parts by weight of ammonium carbonate with stirring, and using about 50 parts by weight of 28% ammonia water to adjust the pH.
Is gradually added until it becomes 9 to 10 to obtain a transparent aqueous solution of 16% by weight of zinc ammonium carbonate (zinc concentration is 4.5%). This zinc ammonium carbonate (b)
The compounding ratio is 0.1 to 1. 1 as a molar ratio of zinc to the total amount of unsaturated carboxylic acid in the acrylic emulsion (a).
When the amount of the compound is 0 mol, the water-resistant adhesive strength is remarkably improved by the chelate reaction between the carboxyl group and zinc. 0.
When the amount is less than 1 mol, sufficient water resistant adhesive force cannot be obtained, and when the amount is more than equimolar, the solid content and viscosity of the adhesive composition decrease, and at the same time, the water resistant adhesive force is in an equilibrium state and there is no point in increasing the amount.

As described above, the acrylic emulsion composition for wood bonding according to the present invention has a water-resistant adhesive strength in the bonding of plywood and veneer without the use of the conventional amino-based condensation resin of the adhesive, resulting in a work environment. Excellent compatibility with wheat flour used as a bulking agent without any problems, starting with mechanical stability and coatability at the time of coating with a roll coater, etc. Since the cracking occurrence rate is low, its practical value as an adhesive for veneer decorative plywood is extremely high, and its significance is great.

A concrete acrylic emulsion composition for wood adhesion according to the present invention, for example, is prepared by collecting acrylic emulsion (a) having a solid content of 50% in a 1 liter beaker and mixing it with a 16% aqueous solution of zinc ammonium carbonate while stirring. Obtained by mixing with stirring. When bonding the actual plywood and veneer, 100 g of the acrylic emulsion for wood
On the other hand, 10 to 100 g of flour and, if necessary, water are added and uniformly mixed and used. The above 16% aqueous solution of zinc ammonium carbonate may be blended before or after the blending of wheat flour in some cases.

The acrylic emulsion composition for wood adhesion of the present invention contains a preservative, water, and
You may use together a dispersant, a defoaming agent, a film-forming aid, a plasticizer, a coloring agent, polyvinyl alcohol, an antifreezing agent, and an amino-type condensation resin.

[0020]

EXAMPLES Hereinafter, production examples, examples and comparative examples of the present invention will be described. Parts and% in the examples are by weight unless otherwise specified. The numbers in the table represent parts by weight unless otherwise specified. Abbreviations used in the examples are as follows.

Stability indication during emulsion polymerization G: Very little adherence in flask and coarse particles (good) LP: Coarse particles GL: Gelation NP: Unreacted (large amount of residual monomer) Abbreviation of monomer ST: Styrene nBA : N-butyl acrylate N-MAM: N-methylol acrylamide N-MMAM: N-methylol methacrylamide MAM: methacrylamide AA: acrylic acid IA: itaconic acid HEMA: hydroxyethylmethacrylate MMA: methylmethacrylate tDM: tert-do Tesyl mercaptan

Production Examples 1 to 20 A mixture of 100 parts of a mixed monomer for the core and shell layers and a chain transfer agent (tDM) having the composition ratios shown in Table 1 was separately weighed in advance, and 50 parts of distilled water and dodecylbenzene were respectively measured. It was dripped into 0.5 part of sodium sulfonate under a stirrer to obtain a pre-emulsified monomer. Separately, 95 parts of distilled water and 0.1 part of sodium dodecylbenzene sulfonate were charged into a 1 liter flask, and the temperature was raised to 70 ° C. with stirring under a nitrogen blanket.
In order to form 0.5 parts of potassium persulfate and the seed of the emulsion, an equivalent mixed monomer of n-butyl acrylate, methyl methacrylate and hydroxyethyl methacrylate was charged and reacted for 30 minutes to form seeds of emulsion particles. Then, the pre-emulsified monomer for core was continuously added dropwise over 3 hours in proportion to the core / shell ratio shown in Table 1, and the residual monomer was reacted for 1 hour after the addition was completed. Subsequently, the emulsified monomer for shell was added dropwise over the same proportion as described above for 3 hours, and the reaction of the remaining monomer was carried out for 3 hours, followed by 40 ° C.
And cool to pH 5 with 14% aqueous ammonia,
It was filtered through a wire mesh of 00 mesh to obtain an acrylic emulsion having a solid content of 50%.

[0023]

[Table 1]

[0024]

[Table 2]

[0025]

[Table 3]

Examples 1 to 15 Acrylic emulsions obtained in Production Examples 1 to 13 were mixed with a 16% concentration zinc ammonium carbonate aqueous solution (4.5% zinc concentration) in the proportions shown, and used for the wood bonding of the present invention. An acrylic emulsion composition was obtained. This emulsion 100
30 parts of flour (manufactured by Japan Flour Milling Co., Ltd., trade name, red peony (high gluten content product)) was mixed with 30 parts of the mixture to give a viscosity of 5,000.
The adhesive for veneer decorative plywood was adjusted to 10,000 cps. This veneer decorative plywood adhesive spreader 12m
10g per m square plywood shank, cover with 0.25mm thick white oak veneer placed in water beforehand
It was pressed at a pressing pressure of 10 kg / cm ² for 1 minute using a 15 ° C. hot press, cooled to room temperature, and baked and coated with an aminoalkyd resin.

The results of the evaluation tests shown below are shown in Table 2. <Evaluation test> 1. Workability The presence or absence of fluidity when blending flour was visually observed and displayed as shown below. ◯: Easy to mix and has fluidity and sufficient roll coater coating is possible. Δ: Mixable, but roll coater can be coated although it has high viscosity and lacks fluidity. X: Mixing is difficult and powder is left as it is, and roll coater coating is not possible. Possible 2. Second-class immersion peeling test From the sample, a square piece having a side of 75 mm was cut into 4 pieces, immersed in hot water at 70 ° C for 2 hours, and then dried at 60 ° C for 3 hours to obtain a portion of the same adhesive layer which was not peeled off. The length was measured on each side. Judged according to the JAS conformity standard and displayed the number of passing pieces. The JAS conformity criterion is that the length of the non-peeling portion of the same adhesive layer is 50 mm or more on each side surface. 3. 1st type immersion peeling test A sample similar to the 2nd type immersion peeling test was immersed in boiling water for 4 hours, dried in a 60 ° C dryer for 20 hours, then again immersed in boiling water for 4 hours and dried in a 60 ° C dryer for 3 hours. Then, the same evaluation as above was performed and the same display was made. 4. Repeated cold heat test From the above sample, a square piece having a side of 15 cm was cut into two single-sided corners, and dried at 80 ° C for 2 hours and at -20 ° C for 2 hours for 1 hour.
After treating for 2 cycles (8 hours in total), the temperature was returned to room temperature, and the number of dry cracks on the surface of the veneer was measured and displayed. JAS
The conformity criterion is that the test piece does not crack, blister, wrinkle, or the like. ○: No number of dry cracks per area △: 〃 1 to less than 5 places ×: 〃 5 or more places 5. Resin leaching contamination The easiness of peeling from the press plate immediately after hot pressing and the presence or absence of gloss on the surface of the veneer due to resin leaching on the surface of the veneer were observed and displayed as shown below. ◯: Good peeling from the press board and no gloss on the surface of the veneer △: Good peeling from the press board, but a little gloss on the surface of the veneer ×: Hard to peel off from the press board and gloss on the surface of the veneer

[0028]

[Table 4] * Mole number in the 16% aqueous solution of zinc ammonium carbonate is the ratio of the number of moles of zinc to the acrylic monomer having a carboxyl group.

Comparative Examples 1 to 6 Using the acrylic emulsions obtained in Production Examples 14 to 19,
Similar to Example 1, 16% zinc ammonium carbonate and wheat flour were blended in the proportions shown in Table 3, and the mixture was subjected to the same test as in Example 1 and the results are shown in Table 3. In addition, manufacturing examples 20, 21,
In No. 22, the evaluation was stopped due to gelation.

Comparative Example 7 The same test as in Example 1 was carried out except that the 16% zinc ammonium carbonate aqueous solution was removed from Example 1, and the results are shown in Table 3. Comparative Example 8 The 16% aqueous zinc ammonium carbonate solution of Example 1 was subjected to the same test as in Example 1 except that the molar ratio of zinc to the carboxyl group-containing acrylic monomer was 1.5, and the results are shown in Table 3. . Comparative Example 9 The acrylic emulsion used in Example 1 was prepared using styrene-butadiene latex (SBR) (Mitsui Toatsu Chemicals, Inc.).
Made, product name Polylac 750, solid content 48%, viscosity 10
0 cps, pH 7, Tg + 8 ° C, acrylic acid 2%, N-
16% Zinc ammonium carbonate and wheat flour were blended in the same manner as in Example 1 except that methylol acrylic amide was modified to 2%), and the results were obtained by performing the same test as in Example 1.
Shown in 3. Comparative Example 10 A 16% zinc ammonium carbonate aqueous solution was removed from the composition of Comparative Example 9, and an amino-based condensation resin (Mitsui Toatsu Chemicals, Inc., trade name Euroid 310, solid content 50%, viscosity 190 cps) was used instead. The mixture of parts was subjected to the same test as in Example 1 and the results are shown in Table 3.

[0031]

[Table 5] * Comparative Examples 2, 3, 7, 9 Since it is impossible to apply the composition with a roll coater having poor workability, a wood spatula was used to apply the composition onto the adherend.

[0032]

INDUSTRIAL APPLICABILITY The wood-based acrylic emulsion composition for adhesives of the present invention is capable of adhering plywood and veneer without using an amino-based condensation resin unlike conventional adhesives in hot water resistance and boiling resistance. Excellent in. Further, there is no problem in working environment, and it is excellent in miscibility with wheat flour used as a bulking agent. In other words, it has fluidity, including mechanical stability during roll coater application, workability, and stable application to adherends, and especially leaching of adhesive onto the sliced veneer surface and contamination and cracking. Since the incidence is low, it has a high practical value as a wood adhesive, especially as an adhesive for veneer decorative plywood.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takeshi Ito 1190 Kasama-cho, Sakae-ku, Yokohama-shi, Kanagawa Mitsui Toatsu Chemical Co., Ltd. Within the corporation

Claims (6)

[Claims] 1. A core layer is a copolymer of an aromatic vinyl monomer, an unsaturated carboxylic acid ester monomer, an amide group-containing acrylic monomer and an unsaturated carboxylic acid, and a shell layer is an aromatic vinyl monomer, an unsaturated carboxylic acid. Solid content of acrylic emulsion (a) having a two-layer structure, which is a copolymer of an ester monomer and an unsaturated carboxylic acid 1
Zinc ammonium carbonate (b) per 100 parts by weight is added as a zinc in an amount of 0.1 to 1.0 molar ratio with respect to the total amount of the carboxyl group-containing acrylic monomer of the acrylic emulsion (a) for wood adhesion. Acrylic emulsion composition. 2. A core layer of acrylic emulsion (a) /
The acrylic emulsion composition for wood adhesion according to claim 1, wherein the monomer composition ratio of the shell layer is 30 to 70/70 to 30 parts by weight per 100 parts by weight of the total amount of monomers. 3. The glass transition temperature (Tg) of the core layer of the acrylic emulsion (a) is −10 to + 90 ° C., and the glass transition temperature (Tg) of the shell layer is −50 to + 20 ° C. The acrylic emulsion composition for wood bonding according to claim 1. 4. The amount of the amide group-containing acrylic monomer and unsaturated carboxylic acid in the core layer of the acrylic emulsion (a) is 1 per 100 parts by weight of the total amount of the core layer monomers.
The acrylic emulsion composition for wood adhesion according to claim 1, wherein the amount of unsaturated carboxylic acid in the shell layer is 1 to 10 parts by weight per 100 parts by weight of the total amount of monomers in the shell layer. 5. The acrylic emulsion composition for wood bonding according to claim 1, wherein the pH of the acrylic emulsion (a) is adjusted to a range of 4 to 6 using aqueous ammonia. 6. The ammonium zinc carbonate (b) comprises water, ammonium carbonate, zinc oxide and aqueous ammonia 15.
The acrylic emulsion composition for wood adhesion according to claim 1, which is a transparent aqueous solution having a concentration of -20% by weight and having a pH adjusted to 9-10.